Different methods to provide polymers with flame-resistance are known in the art: said methods are generally based on the addition to the polymer of heat-unstable halogenated compounds associated with metallic compounds, expecially antimony and/or bismuth compounds.
Generally, the combinations between metallic compound and halogenated compound give satisfactory results as far as the characteristics of flame-resistance are concerned, but they involve more or less serious inconveniences and particularly:
corrosion phenomena in the equipments wherein the treatment of polymers containing the above mentioned additives is carried out; PA0 worsening in the release of darkening smokes during combustion and/or decomposition of said polymers. PA0 (A) from 60 to 98.9% of a synthetic thermoplastic polymer; PA0 (B) from 0.1 to 10% of at least a product selected from antimony oxide, antimony oxychloride, antimony trisulfide, metal bismuth and an organic or inorganic, oxygenated or non-oxygenated bismuth salt; PA0 (C) from 0 to 1% of a promotor of free radicals; PA0 (D) from 1 to 30% of melamine bromohydrate.
It is also known that ammonium salts of hydroacids generally have an effective action as flame-retarders in many fields such as the field of paints and coatings, but they cannot be used directly as additives in thermoplastic polymers due to their high corrosive action with respect to metals, their extreme sensitivity to water and air humidity and their poor thermal and thermo-oxidizing stability.